tom,hi i'm paul.the a15 valve sizes are from a gregory's for the 120y,which also lists a13's,a14's & A15's.so if i can't trust the gregory's that doesn't surprise me.as for pictures of my 1000 & the 1200's,the scanner is here,i just need learnin up on how to use it.also have the video of me rolling my 1200 at huntley colliery hillclimb,so one day i might figure out how to download that.wayne,as for the gearbox theory,that was past on to me from someone in south aus who made close ratio gearsets for the 1200 boxes.as i personally blown up both 1200 & 120y boxes,i much prefer the a14 sizes.surprisingly,yes,the only a12 box that seemed to last was a 120y 4 speed,but this was in front of an a12,not an a15 like the previous ones.the theory was the needle roller in the 120y box was a limitation.

My experience tells me that there were 2 different 120Y gearboxes. I think it was the idler gear shaft had bushes and another had bearings. The bushes and bearings were different sizes. So it's not just a matter of putting bearings in. Although you might be able to get replacement bearings to suit.

Sorry I have no information on how to tell the difference externally. Just something I thought I'd share on this gearbox discussion.

Chris.

tom,checked that gregory's again for you,the a14/a15 has 37 mm inlets & 30 mm exhaust valves.i can remember years ago a friend put a14 inlet valves into a 1200 gx head,but didn't worry about the exhaust as they weren't big enough to worry about.this sorta corresponds to the sizes above.apologies for the blunder.

YAY!! She runs!!
I hadnt been able to get it fired up since I got the head back on, and I must admit it was a bit of a headscratcher! it had spark, it had compression , I did the valve lashes, it had to have fuel because I just bought a new carby!
but I realised I hadnt remembered to line number 1 plug on the dizzy with TDC when I put it back in! she fired pretty much straight away and runs smoothly.
I love the sound of that weber!